The present invention relates generally to automation systems, and more particularly to an expandable automation system. Automation systems on the market today can be divided into two groups, namely programmable controllers of a modular construction and programmable controllers capable of autonomous or stand-alone operation. The latter can be expanded by connecting peripheral equipment. Both types of programmable controllers, however, have disadvantages specific to their group.
Programmable controllers that are capable of stand-alone operation, so-called compact units, are in fact relatively inexpensive when first installed. However, when the level of automation is increased later on, they reach their limits very quickly, with respect to the compact unit's expanding capability as well as its computing power. Therefore, when later expansion is required, the entire programmable controller often has be replaced by a programmable controller with a modular design.
Modular automation systems, such as that disclosed by German Published Patent Application 36 03 750, avoid these disadvantages. However their minimal configuration, consisting of a central processing unit and a few expansion modules, is often considerably more expensive than a compact unit.
The present invention is directed to the problem of developing an automation system, which is suited both for small automation tasks as well as for larger automation tasks and which can be adapted at any time to modified requirements resulting from future expansion.